JP2524072B2 - Method and apparatus for manufacturing glass composites - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention melts at least two starting materials having different material compositions, supplies the starting materials to a drawing nozzle arranged at the bottom of an outer melting crucible, and is horizontal to the drawing direction. Method for producing an elongated composite material made of glass by continuously and vertically drawing a melt from a drawing nozzle while forming a laminated composite material and a melting crucible having a drawing nozzle at the bottom and a melting crucible And a supply device for supplying at least two starting materials having different material compositions.

[0002]

2. Description of the Prior Art Such a method and a device for carrying out the method are known, for example, from DE-A-2703706. The specification describes a method for continuously producing an optical waveguide for optical communication engineering, the waveguide comprising a core glass, a core glass surrounding the core glass and a lower refractive index than the core glass. It is made of clad glass. In the method, the optical waveguide is pulled from a so-called double crucible. The double crucible consists of an outer crucible that is heated on the outside and that contains the clad glass melt.In the outer crucible, the inner crucible containing the core glass melt is concentrically arranged, and the side wall of the inner crucible is It projects above the melt surface of the clad glass melt. A drawing nozzle is provided at the bottom of the outer crucible. Perpendicular to the upper side of the drawing nozzle, an outlet opening is provided in the bottom of the inner crucible, the outlet opening of the inner crucible plunging into the cladding glass melt and thus the core glass melt released from the inner crucible. It is surrounded on all sides by the clad glass melt and is ejected from the drawing nozzle of the outer crucible. The charging of the inner and outer crucible composite-starting material is carried out independently and separately from one another by continuously feeding back glass rods of the starting material into the respective melts. The outer and inner crucibles consist of platinum plates in the known device.
It is known that platinum begins to melt in glass above 900 ° C. Furthermore, it is possible to strip the platinum particles from the crucible wall and together with the melt flowing along the crucible wall.

EP-A-0185362 describes a device for the continuous production of optical fibers of two different substances.
Glass-forming composite material-the starting material and the dopant in reactive and liquid form are fed at room temperature into a double crucible. The inner and outer crucibles of the double crucible are arranged concentrically with each other and their conically tapering bottoms are arranged vertically one above the other. The inner crucible is vertically movable within the outer crucible. The upper part of the double crucible, in which the liquid starting materials react with each other to form a partially solidified mass, is surrounded by a curing oven, the temperature of which rises from room temperature to the curing temperature from top to bottom. The lower part of the outer crucible reaches the second furnace, which likewise has in the lower part a maximum temperature sufficient to soften the composite material so that the fibers can be taken out of the drawing nozzle of the outer crucible. It has a temperature gradient from top to bottom.

A known method of producing composite materials made of glass is to melt or combine two starting materials for producing the composite material in separate crucibles, one crucible of the other crucible. It is arranged internally as an inner crucible and shares that at least one outlet opening projects into a second liquid or mucous starting material. This results in a reaction with the inner crucible material, especially in the case of high temperatures and corrosive starting materials, which results in, for example, wear or non-uniformity of the inner crucible at the inner crucible and composite-starting material contact surfaces. This may occur, for example bubbles. This non-uniformity or contaminant enriches at the interface of different starting materials after withdrawal of the composite material. In this case it is generally particularly harmful.

In the known method, a frame with a constant spatial distribution of the two starting materials inside the composite material is obtained due to the distance between the outlet opening of the inner crucible and the withdrawal nozzle of the outer crucible and the change in the shape of the nozzle opening. Adjustable within. However, the double crucible construction required for this or the necessary retrofitting measures is expensive. Furthermore, in adjusting the size of the nozzle opening, the melt is drawn concentrically inside the outer crucible and thus inside the relatively cold region of the melt, taking into account the viscosity of the melt as it is drawn. Care should be taken not to block the crucible outlet opening.

If the inner and outer crucibles are maintained at a constant temperature and at a fixed spatial ratio to each other, the spatial distribution of the starting materials within the composite material is such that the filling position height of the melt in each crucible is It is a function of (at the same pressure and in the molten state). If the spatial distribution of the starting materials in the composite material should be constant, then the problem of maintaining the melt liquid level heights at a constant level or at a constant ratio to one another arises.

[0007]

The object of the present invention is to enable the formation of a uniform, contaminant-free interface of the starting materials within the composite material, and the composite material--the composite material between the materials-- It is to provide a method for producing a composite material made of glass of the type described at the outset, in which the extension of the interface can be formed in a simple way and with many degrees of freedom,
And to produce a composite material, which is particularly suitable for producing a composite material at high temperatures and which allows the formation of a composite material-interface in a simple manner and with a large number of degrees of freedom, Was to provide the device.

[0008]

According to the invention, in view of the method, said object is to continuously feed the starting material in the form of particles to only one melting crucible and to deposit the precursor in the melting crucible, In this case, a starting material having one composition is present adjacent to a starting material having the other composition at a boundary surface extending substantially parallel to the drawing direction, and the precursor is taken out by a drawing nozzle. The starting material is fed into a single melting crucible and is deposited on the precursor so that the starting material of one composition lies adjacent to the starting material of the other composition at an interface extending substantially parallel to the drawing direction. This avoids that the starting material interface forms a surface or contact surface for the crucible material. In the known method, non-uniformities in the interface area of the contaminants or composite material, such as those caused by crucible material, are thereby completely eliminated. By continuously supplying the starting material in the form of particles to a melting crucible and depositing the precursor in the crucible, in a predeterminable, planar distribution of the various starting materials, each of the material properties can be adjusted to any desired value. The spatial distribution is adjustable, in which case the solids of the starting materials are agglomerated to a large extent when they are fed to the melting crucible, thereby avoiding mutual inclusions. By using a common melting crucible for the various starting materials, the spatial distribution of the starting materials within the composite is independent of the height of the deposit in the melting crucible. The melting of the particulate starting material in the melting crucible occurs first in the region of the precursor, and thus in the region where the starting material of one composition is adjacent to the starting material of the other at the interface and withdrawal of the melting crucible. It is carried out at a temperature such that its viscosity in the area of the nozzle is so low that it does not block the drawing nozzle. In some cases, the draw-out nozzle, which is easily accessible from the outside, can additionally be heated.

The process according to the invention is formed in a particularly advantageous manner when quartz glass or high silicic acid-containing glass is used as starting material. The starting materials may then differ, for example, in terms of purity or doping material concentration. Due to the low dependence of viscosity on temperature, a layered flow ratio can be obtained inside the melting crucible even with a relatively steep temperature gradient using quartz glass or high silicic acid-containing glass, and
The contamination of the starting material in the region of the interface is largely avoided.

When the starting material is fed to the melting crucible via outlet openings which are arranged concentrically to one another, the deposition is carried out particularly uniformly, the outlet openings being viewed in the direction of the particulate starting material feed. And may have any cross section. This largely prevents the contamination of starting materials.

The melt of the starting material is drawn out into a multi-layer tube through a drawing nozzle formed in the shape of a ring,
The way in which gas can be introduced inside the tube has been shown to be particularly advantageous.

It has proved to be particularly advantageous to feed the melting crucible with a starting material having a particle size of 20 μm to 2 mm and in particular 100 μm to 300 μm. The use of corresponding flowable or flowable particles ensures, on the one hand, a uniform supply of the starting material to the melting crucible and a uniform packing of the melting crucible, and on the other hand the individual starting material particles in their interface region. Contamination is largely avoided. In this connection, it has been shown to be particularly advantageous to select the particle size distribution of the starting materials of the composite material as narrow as possible and almost uniform for all starting materials.

It has been shown to be advantageous to maintain a temperature gradient with a rising temperature in the drawing direction of the composite material over the height of the melting crucible. The rate of the diffusion process of the components of one starting material into the other and the incorporation of one starting material and the other starting material depends to a great extent on the temperature in the melting crucible. The formation of a temperature gradient across the height of the melting crucible ensures that such a process, if at all, proceeds first in the area immediately around the draw nozzle and avoids the incorporation of large amounts of starting material. To be done.

The starting material is preferably preheated in a melting crucible,
And supply under protective gas. Preheating of the particulate starting material removes surface-bound contaminants such as water.
By feeding the starting material into the melting crucible under protective gas, the ingress of gaseous pollutants into the starting material in the hot furnace atmosphere is avoided. At the same time, the flow of protective gas makes it possible, if necessary, to adjust the overpressure in the melting crucible. This has been shown to be advantageous for maintaining a uniform laminar flow of the starting material in the direction of the draw nozzle. The required overpressure level in the melting crucible depends, for example, on the viscosity of the starting material in the region of the drawing nozzle, on the particle size distribution used and on the desired drawing speed of the composite material from the melting crucible.

With regard to the device, the problem is that the device according to the invention has only one melting crucible with an extraction nozzle arranged at the bottom and the particulate starting material is appropriately fed to a predetermined region of the melting crucible. In order to achieve this, it is solved by providing a respective supply device for the respective material composition. A device with only one melting crucible is particularly simple and has few failures. Furthermore, the only outlet opening for the melt of the starting material, the withdrawal nozzle, is arranged in a good accessible manner at the bottom of the melting crucible and, if appropriate, can be easily cleaned or replaced.
Between the starting materials inside the melting crucible, and thus in the composite material, by means of a respective supply device for each material composition in order to properly supply the particulate starting material to the defined regions of the melting crucible. The extension of the boundary surface between the substances can be formed with a large degree of freedom by a simple method. In this case, the feeding device makes it possible to distribute the starting materials to their respective compositions and to distribute them planarly inside the melting crucible, but during melting either outside the melting crucible itself or at least above the melt. It is a device placed in.

For uniform deposition in the melting crucible and proper supply of the starting materials, at least at the end facing the melting crucible, there are conduits arranged coaxially to one another, wherein
It has proved to be particularly advantageous for the feed device to feed the starting material into the melting crucible through the tube openings or the gaps of the tubes arranged concentrically with each other.

A particularly simple possibility for adjusting the spatial distribution of the starting material in the melting crucible holds in the case of a feeder in which the conduit is kept vertically movable. The conduits are then preferably movable to the bottom of the melting crucible and to each other.

The end of the tube facing the melting crucible is formed by conically expanding or conically tapering, whereby:
The maximum outer diameter of the inner tube in the region of the extension of the cone is greater than the minimum inner diameter of the adjacent and further outer conduits, thereby moving the conduits perpendicularly to each other, thereby reducing the gap opening of the pipes and thus the various openings. It is possible to vary the amount of starting material supplied in a simple manner.

An arrangement is advantageous in which the draw-out nozzle has a ring-shaped outlet opening at the bottom of the melting crucible, the gas supply pipe extending through the melting crucible in the center of the outlet opening. In this case, the circular central part of the drawing nozzle can be held particularly simply by the lower end of the gas supply pipe, which central part is also connected to the outer ring of the drawing nozzle via a plurality of webs. It may be connected. This configuration of the apparatus for producing glass composites is suitable for producing composites in the form of multi-layer tubes.

In a preferred construction of the device, the withdrawal nozzle projects into a hollow chamber which is flushed with protective gas and which is open in the withdrawal direction. The cavity prevents wet or reactive atmospheres from entering the still hot surface of the composite during the first cooling step.

Molten crucibles containing tungsten or molybdenum have been shown to be particularly trouble free, easy to maintain and abrasion resistant. In some cases it is necessary to protect the melting crucible wall before the ingress of reactive gas. In that respect, it is advantageous to form the melting crucible in a sealable manner. Ingress of moist air or gas that reacts with the hot melt crucible material is thereby avoided. Furthermore,
Overpressure in the melting crucible can be maintained if desired.

[0022]

The present invention will be described in detail with reference to the following drawings.

The apparatus shown in FIG. 1 has a melting crucible 1 with a draw-out nozzle 3 at the bottom 2 of the crucible. A ring-shaped outlet opening 4 is provided in the drawing nozzle 3. A supply device 6 for particulate matter is arranged above the melting crucible 1 inside a heatable ring furnace 5. The feeding device 6 has three substantially inwardly arranged coaxially with each other and has vertically movable conduits 7, 8 and 9, the ends of the conduits facing the melting crucible 1 expanding conically. Or tapering conically, in each case in the end region of the cone the respective inner conduit 7,
8 has a maximum outer diameter of 8
Larger than the minimum inner diameter of. The conduits 7, 8, 9 serve as a supply device for the particulate starting materials 14, 15 to be supplied to the melting crucible 1. A supply conduit 10 for the protective gas extends inside the innermost conduit 7, which extends through the melting crucible 1 and through the withdrawal nozzle 3 to a hollow chamber 11, which The drawing nozzle is stuck in. The hollow chamber 11 has an opening 12 on the side opposite to the drawing nozzle 3, through which the composite material 13 is drawn using a drawing device 16. At this time, the drawn-out composite material 13 passes through the guide device 17 and the thickness measuring device 18. The melting crucible 1 is made of tungsten and can be pressure-tightly closed by a cover plate 23 through which the conduits 7, 8, 9 of the supply device 6 pass in a vacuum-tight manner. Heating element 19
The outside is closed by a heat insulating layer 20.

In the following, the method of manufacturing the glass composite material according to the invention is typically described using the apparatus shown in FIG. 2 into melting crucible 1 via conduits 8 and 9
Starting materials 14 and 15 having different material compositions are supplied.
Starting materials 14 and 15 have a particle size distribution of 100 μm to 300 μm.
m is a particulate quartz glass. A starting material 15 made of natural quartz glass is fed to the melting crucible 1 via a conduit 9 and a starting material 14 made of synthetic quartz glass of high purity is fed via a conduit 8. The conduits 7, 8, 9 are used to feed the quartz glass-starting materials 14, 15 into the melting crucible 1 in predetermined areas. In this case, the precursor 21 is continuously deposited in the melting crucible 1 and the quartz glass particles 14 of one composition are deposited on the other at the boundary surface 36 extending substantially parallel to the drawing direction characterized by the arrow 22. Quartz glass particles of composition 1
It exists adjacent to 5. The precursor 21 is heated in the melting crucible 1 while forming a melting front 35 extending below the supply device 6, the temperature of the ring furnace 5 being 180 °.
It is 0-2300 degreeC. Thereby, the viscosity of the precursor 21 is the lower part of the melting crucible 1, the precursor 21 is supplied to the drawing nozzle 3, and 2 m / h-3 by the drawing nozzle.
Outer diameter of 15 in drawing direction 22 at a drawing speed of m / h
Ring-shaped composite material 2 with 0 mm and wall thickness 20 mm
It decreases as it is pulled out as 1.

The layer thickness ratio of the composite material 13 depends on the amount ratio of the starting materials 14, 15 supplied to the melting crucible 1. This quantity ratio is due to the vertical movement of the conduits 7, 8, 9 and the respective conduit 7,
0-100 depending on the change of the gap opening 24, 25 between 8 and 9.
It can be adjusted to the value of%. For example, at the beginning of the manufacturing process, in the empty melting crucible 1, the innermost conduit 7 is lowered to the conically tapering inner surface of the conduit 8, thereby closing the gap 24 between the conduits 7, 8 and The supply of quartz glass particles 14 from the conduit 8 to the melting crucible 1 is blocked. At the same time, by raising the intermediate conduit 8, the gap 25 between the outer surface of the conduit 8 and the inner cross section of the inwardly tapered conduit 9 can be increased. Thereby, before opening the gap 24 between the inner surface of the conduit 8 and the outer surface of the conduit 7, the melting crucible 1 is first supplied with cheaper vitreous silica and the melting crucible is made into a corresponding quartz glass. Particle 1
Fill with 5. This first particle packing is withdrawn in a preliminary stage, during which thermal equilibrium occurs in the melting crucible 1. However, the conduits 7, 8 and 9 are lowered to the bottom 2 of the melting crucible 1 at the start of the manufacturing process of the composite material 13, and the precursor 21 is formed, while the silica glass particles 14 and 15 are continuously connected by the gaps 24 and 25. Precursor 2
It is also possible to gradually raise 1 to the desired height.

The process described above is used to produce composite tubes having a high-purity synthetic quartz glass inner layer and a quartz glass outer layer of natural crude, for example used as diffusion tubes for semiconductor products. It is possible to Another one
One example of use is the use of corresponding glass compositions to make composite tubes for lamp cladding tubes made of fused silica with a doped outer layer and an undoped inner layer.

In the embodiment of the device according to the invention shown in FIG. 2, the draw-out nozzle 26 arranged at the bottom of the melting crucible 1 has a circular opening 27. A rod-shaped composite material 28 is pulled out using a pulling device 16 from a circular opening 27 having a diameter of 100 mm. The supply device 6 in this embodiment comprises two conduits 29, 30 arranged coaxially to one another and movable perpendicular to one another, the lower end of which is facing the melting crucible 1. Each is enlarged in a cone shape. The maximum outer diameter of the inner tube 29 is chosen to be larger than the inner diameter of the outer tube 30 and thus the two conduits 2
The gap 31 of 9, 30 can be moved by raising the inner conduit 29. Pure synthetic particulate silica glass 32 in the melting crucible 1 via the gap 31 between the conduits 29, 30.
And silica glass 33 doped with particulate germanium via conduit 29 and deposited on the precursor 34 in the melting crucible 1. The particulate quartz glass-starting material 32, 33 is then fed to the melting crucible 1 under protective gas and preheated at a temperature of about 500 ° C. Water adhering to the quartz glass particles 32, 33 by preheating is removed before the starting materials 32, 33 are introduced into the melting crucible 1. Overpressure is maintained by introducing the starting materials 32, 33 under protective gas and by expanding the protective gas into the melting crucible 1 which is pressure-tightly closed by a cover plate 23. The precursor 34 is heated to a temperature of about 2200 ° C. in the area of the draw nozzle 26.

In FIGS. 1 and 2, parts corresponding to each other are designated by the same reference numerals. Thus, device parts not described in detail in FIG. 2 may be assigned corresponding reference numerals and descriptions in FIG. The device shown in FIG. 2 can be used, for example, to withdraw preforms from which optical waveguides can be produced for optical communication engineering.

[Brief description of drawings]

1 is a cross-sectional view of an apparatus for producing a tubular composite material according to the present invention.

FIG. 2 is a sectional view of an apparatus for producing a rod-shaped composite material according to the present invention.

[Explanation of symbols]

1 Melting crucible, 3,26 Drawing nozzle, 6
Supply device, 7, 8, 9 conduits, 11 hollow chambers, 1
4,15 starting material, 21,34 precursor, 22
Drawing direction, 36 boundary surface

Claims (19)

(57) [Claims] 1. A composite in which at least two starting materials having different material compositions are melted, the starting materials are supplied to a drawing nozzle arranged at the bottom of an outer melting crucible, and stacked horizontally with respect to the drawing direction. In a method for producing an elongated composite material made of glass by continuously and vertically drawing a melt from a drawing nozzle while forming the material, the starting material (14, 15) is continuously fed and the precursors (21, 34) are deposited on the melting crucible, at the interface (36) extending substantially parallel to the drawing direction (22),
A composite material made of glass, characterized in that a starting material (14) of one composition is present adjacent to a starting material (15) of the other composition and the precursor is extracted by means of an extraction nozzle (3.26). A method of manufacturing. 2. The method according to claim 1, wherein quartz glass or high silicic acid-containing glass is selected as the starting material (14, 15). 3. Outlet openings (2) arranged concentrically with one another in a crucible (1) for melting the starting materials (14, 15).
4. The method according to claim 1 or 2, which is supplied via 4. A double-walled pipe (1) with a starting material (14, 15) through a ring-shaped drawing nozzle (3).
Method according to any one of claims 1 to 3, which is drawn out in 3). 5. The method according to claim 4, wherein a gas is introduced inside the tube. 6. The process according to claim 1, wherein starting materials (14, 15) having a particle size of 20 μm to 2 mm are used. 7. The method according to claim 6, wherein a particle size of 100 μm to 300 μm is selected. 8. The method according to claim 1, wherein a temperature gradient is maintained across the height of the melting crucible (1), the temperature gradient increasing in the direction of withdrawal (22) of the composite material (13, 28). The method according to item 1. 9. Starting materials (14, 15) are preheated in a melting crucible (1) and / or fed under protective gas.
Method according to any one of claims 1-8. 10. Starting material (1) in a melting crucible (1)
Method according to any one of claims 1 to 9, wherein overpressure is applied to 4,15). 11. An apparatus for producing an elongated composite material made of glass, comprising a melting crucible having a drawing nozzle at the bottom and a feeding device for feeding at least two starting materials of different material composition to the melting crucible, The device has a unique melting crucible (1) with a draw nozzle (3, 26) located at the bottom, and a particulate starting material (14, 15) in a defined area of the melting crucible (1). Device for producing a composite material made of glass, characterized in that a supply device (6) is provided for each substance composition in order to supply properly. 12. The supply device (6) comprises conduits (7, 8, 9).
Device according to claim 11, characterized in that the conduits are arranged coaxially to each other, at least in the end region facing the melting crucible (1). 13. Device according to claim 12, in which the conduits (7, 8, 9) are held movably in the vertical direction. 14. The end of the tube facing the melting crucible (1) is formed such that it conically expands or tapers in the shape of a cone, the outermost part of the inner tube (7, 8) being the largest outside. Device according to claim 12 or 13, wherein the diameter is larger than the smallest inner diameter of the tubes (8, 9) lying adjacent and further outside. 15. The device according to claim 11, wherein the withdrawal nozzle (3) is formed with a ring-shaped outlet opening. 16. Device according to claim 15, characterized in that the gas supply pipe (10) extends from the outside of the melting crucible (1) through the withdrawal nozzle (3) concentrically to the outlet opening. 17. The device according to claim 11, wherein the withdrawal nozzle (3) is flushed with gas and projects into a hollow chamber (11) which is open in the withdrawal direction (22). 18. Device according to claim 11, wherein the melting crucible (1) consists of tungsten or molybdenum. 19. The device according to claim 11, wherein the melting crucible (1) is hermetically formed.